Semiconductor device using metal nitride as insulating film and its manufacture method

ABSTRACT

A first insulating film is formed on a semiconductor substrate. A second insulating film made of insulating metal nitride is formed on the first insulating film. A recess is formed through the second insulating film and reaches a position deeper than an upper surface of the first insulating film. A conductive member is buried in the recess. A semiconductor device is provided whose interlayer insulating film can be worked easily even if it is made to have a low dielectric constant.

CROSS REFERENCE TO RELATED APPLICATION

This application is a division of application Ser. No. 11/822,463, filedJul. 6, 2007 which is a continuation of application Ser. No. 11/362,872,filed on Feb. 28, 2006, now U.S. Pat. No. 7,256,500 which is acontinuation of application Ser. No. 10/352,149, filed on Jan. 28, 2003,now U.S. Pat. No. 7,042,093, which is based on Japanese PatentApplication No. 2002-133055, filed on May 8, 2002, the entire contentsof which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1) Field of the Invention

The present invention relates to a semiconductor device and itsmanufacture method, and more particularly to a semiconductor devicehaving the wiring structure formed by burying conductive material in atrench formed through an insulating film above a semiconductorsubstrate.

2) Description of the Related Art

Development of processing techniques of large scale integrated circuitdevices (LSI) makes each semiconductor element increasingly smaller.High density, multi-layers and thinning of wiring lines in LSI areadvancing so that stress applied to the wiring lines and the density ofcurrent flowing in the wiring lines are increasing more and more. As thedensity of current flowing in a wiring line increases, electromigration(EM) is likely to occur so that a wiring line may be broken. It isconsidered that electromigration occurs because electrons transported ina wiring line collide with metal atoms constituting the wiring line andthe metal atoms move or diffuse. As semiconductor elements are madefiner, the deterioration of elements by electromigration becomesserious. It is necessary to develop the wiring material and wiringstructure which have a high reliability and can suppresselectromigration even if current of a high density is flowed.

Copper is wiring material which is more resistant againstelectromigration than aluminum. However, a copper layer is difficult tobe finely worked more than an aluminum layer. A damascene method ispractically used as an effective method of forming a wiring line.According to the damascene method, a wiring trench is formed beforehandthrough an insulating film, copper is buried in this trench, andunnecessary copper is removed to form a wiring line. A dual damascenemethod is also known by which upper and lower wiring trenches and a viahole connecting the trenches are formed and wiring material is buried inthe wiring trenches and via hole at the same time.

High integration and miniaturization of LSI actualize a delay of anelectric signal conveyed in a wiring line. In order to reduce atransmission delay of an electric signal, it is important to lower theresistance of wiring material and the dielectric constant of aninterlayer insulating film. If low dielectric constant material is usedfor an interlayer insulating film, it becomes more difficult to formwiring trenches and via holes than using conventional materials of aninterlayer insulating film such as undoped silicate glass (siliconoxide, hereinafter abbreviated to USG) and fluorine-doped silicate glass(SiOF, hereinafter abbreviated to FSG).

Known insulating film materials having a low dielectric constant includeorganic polymer having carbon as its main composition, carbon-containingsilicon oxide, and porous materials of these materials. If such lowdielectric constant insulating materials are used for an interlayerinsulating film, the following problems occur.

First, tight adhesion of an interlayer insulating film to an etchingstopper layer, a cap layer, a sacrificial film under chemical mechanicalpolishing, and a hard mask such as an insulating film and a barriermetal layer is degraded. If stress in terms of thermodynamics isgenerated during processes such as CMP, heat treatment and bonding,films are likely to be scaled off.

Second, an etching selectivity is lower between an interlayer insulatingfilm and an etching stopper layer of silicon nitride, silicon oxide,silicon carbide or the like and a hard mask. It is therefore difficultto pattern an interlayer insulating film made of low dielectric constantinsulating material.

Third, if an interlayer insulating film is made to have a low dielectricconstant, a mechanical strength and a thermal stability of theinsulating film are degraded. The insulating film may be broken duringmanufacture processes.

Fourth, if an insulating film is made of porous material, the insulatingfilm is likely to be subjected to secular change and deteriorationbecause of the absorption of moisture in the air, oxidation via finevoids and the like.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a semiconductor device andits manufacture method capable of easily working an interlayerinsulating film even if the film is made to have a low dielectricconstant.

According to one aspect of the present invention, there is provided asemiconductor device comprising: a first insulating film formed on asemiconductor substrate; a second insulating film consisting ofinsulating metal nitride and formed on said first insulating film; arecess formed through said second insulating film and reaching aposition deeper than an upper surface of said first insulating film; anda conductive member filled in said recess.

The semiconductor device constructed as above can be manufactured byforming the recess in the first insulating film by using the secondinsulating film of metal nitride as a mask.

According to another aspect of the present invention, there is provideda semiconductor device comprising: a lower wiring layer containing aplurality of wiring lines and formed on a semiconductor substrate; anupper wiring layer containing a plurality of wiring lines and formed onsaid lower wiring layer; and an interlayer insulating film disposedbetween said lower and upper wiring layers and consisting of insulatingmetal nitride.

A dielectric constant of the interlayer insulating film can be loweredby using metal nitride as the material of the interlayer insulating filmmore than using silicon oxide. Since tight adhesion to anotherinsulating film is good, reliability of the semiconductor device can beimproved.

According to another aspect of the present invention, there is provideda method of manufacturing a semiconductor device, comprising steps of:forming a first insulating film consisting of insulating material on asemiconductor substrate; forming a second insulating film consisting ofinsulating metal nitride on said first insulating film; patterning saidsecond insulating film; and etching said first insulating film by usingsaid second insulating film as a mask.

An etching selectivity between an interlayer insulating film made ofmetal nitride and an insulating film containing silicon and carbon asits main composition can be made large. The interlayer insulating filmmade of metal nitride can be easily worked.

According to another aspect of the present invention, there is provideda method of manufacturing a semiconductor device, comprising steps of:forming a first insulating film on a semiconductor substrate, at least asurface layer of said first insulating film consisting of metal nitride;forming a second insulating film consisting of inorganic insulatingmaterial containing silicon on said first insulating film; forming arecess in a lamination structure of said second and first insulatingfilms; depositing a conductive film consisting of conductive material onsaid second insulating film, said conductive film being filled in saidrecess; and polishing said conductive film until said second insulatingfilm is exposed, and leaving a portion of said conductive film in saidrecess.

The first insulating film made of metal nitride is covered with thesecond insulating film during the process of polishing the conductivefilm. The first insulating film is not exposed to polishing liquid andthe like.

As above, by using the insulating metal nitride as a mask for etchingthe insulating film made of low dielectric constant insulating material,the etching selectivity can be made large so that the insulating filmcan be easily worked.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a semiconductor device according toa first embodiment.

FIGS. 2A to 2J are cross sectional views of a substrate illustrating amethod of manufacturing the semiconductor device of the firstembodiment.

FIG. 3 is a cross sectional view of a semiconductor device according toa second embodiment.

FIG. 4 is a cross sectional view of a semiconductor device according toa third embodiment.

FIGS. 5A to 5E are cross sectional views of a substrate illustrating amethod of manufacturing the semiconductor device of the thirdembodiment.

FIG. 6 is a cross sectional view of a semiconductor device according toa fourth embodiment.

FIG. 7 is a graph showing the breakdown voltage characteristics of asilicon/USG/copper structure and a silicon/USG/ZrN/copper structure.

FIG. 8 is a graph showing the breakdown voltage characteristics of asilicon/USG/copper structure, a silicon/thermally oxidized film/copperstructure, and a silicon/USG/ZrN/copper structure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a cross sectional view of a semiconductor device according toa first embodiment. An element separation insulating film 2 is formed onthe surface of a semiconductor substrate 1 of p-type silicon, activeregions being defined by the element separation insulating film 2. A MOStransistor 3 is formed in the active region. The MOS transistor 3 isconstituted of a gate insulating film 3 a, a gate electrode 3 b andimpurity doped regions 3 c and 3 d. One of the impurity doped regions 3c and 3 d is a source region and the other is a drain region.

The impurity doped regions 3 c and 3 d are formed in the substratesurface layer on both sides of the gate electrode 3 b and have a lightlydoped drain (LDD) structure. Sidewall spacers 3 e made of insulatingmaterial are formed on the sidewalls of the gate electrode 3 b. Thesidewall spacers 3 e are used as a mask when ions are implanted in highconcentration regions of the impurity doped regions 3 c and 3 d.

A first interlayer insulating film 4 of silicon oxide (SiO₂) is formedon the semiconductor substrate 1, covering the MOS transistor 3. Contactholes 4 a and 4 b are formed through the first interlayer insulatingfilm 4 in the areas corresponding to the impurity doped regions 3 c and3 d. Conductive plugs 5 a and 5 b are buried in the contact holes 4 aand 4 b. Each of the plugs 5 a and 5 b is constituted of a barrier metallayer of titanium nitride (TiN) covering the sidewall and bottom of theplug and a tungsten member formed on the barrier metal layer.

A first layer wiring pattern 7 made of tungsten is formed on the firstinterlayer insulating film 4. This wiring pattern 7 is connected to theimpurity doped region 3 d of the MOS transistor 3 via the plug 5 b.

On the first interlayer insulating film 4, a second interlayerinsulating film 8 is formed covering the first wiring pattern 7. Thesecond interlayer insulating film 8 is made of silicon oxide,borophosphosilicate glass (BPSG), or phosphosilicate glass (PSG). Acontact hole 8 a is formed through the second interlayer insulating film8 in the area corresponding to the plug 5 a. A conductive plug 9 isburied in this contact hole 8 a.

These structures described above can be formed by well known thin filmforming techniques, photolithography, ion implantation, chemicalmechanical polishing (CMP) and the like.

A third interlayer insulating film 10 of low dielectric constantinsulating material and a first mask layer 11 of high resistancezirconium nitride are formed on and above the second interlayerinsulating film 8. The insulating film material having a low dielectricconstant includes organic polymer having carbon as its main composition,carbon-containing silicon oxide, and porous materials of thesematerials. Wiring trenches 10 a and 10 b are formed through the thirdinterlayer insulating film 10 and first mask layer 11. Second layerwiring patterns 12 a and 12 b are buried in the wiring trenches 10 a and10 b.

Each of the wiring patterns 12 a and 12 b has a three-layer structuremade of a barrier metal layer covering the side wall and bottom of thewiring trench 10 a, 10 b, a seed layer covering the surface of thebarrier metal layer, and a main wiring material member filled in thewiring trench and covering the seed layer. The barrier metal layer ismade of tantalum (Ta), tantalum nitride (TaN), titanium nitride (TiN) orthe like. The barrier metal layer may have a lamination structure of aTa layer and a TaN layer. The seed layer and main wiring material memberare made of copper or alloy containing copper as its main composition.

On and above the wiring patterns 12 a and 12 b and first mask layer 11,an etching stopper layer 15, a fourth interlayer insulating film 16 anda second mask layer 17 are laminated in this order The etching stopperlayer 15 is made of silicon carbide (SiC) or silicon nitride (SiN). Thefourth interlayer insulating film 16 is made of low dielectric constantinsulating material. The second mask layer 17 is made of high resistancezirconium nitride.

A wiring trench 18 is formed in the second mask layer 17 and fourthinterlayer insulating film 16 to the intermediate depth of the fourthinterlayer insulating film 16. A via hole 19 is formed in the fourthinterlayer insulating film 16 and etching stopper layer 15, the via holeinterconnecting the bottom of the wiring trench 18 and the upper surfaceof the second wiring pattern 12 a.

A third layer wiring pattern 20 is buried in the wiring trench 18 andvia hole 19. The third wiring pattern 20 is constituted of a barriermetal layer covering the side wall and bottom of the wiring trench 18and via hole 19, a seed layer covering the barrier metal layer, and amain wiring material member buried in the wiring trench 18 and via hole19 and covering the seed layer. The materials of the barrier metallayer, seed layer and main wiring material member are the same as thoseof the second wiring pattern 12 a.

A cover layer 21 of zirconium nitride is formed on the second mask layer17 and third wiring pattern 20. A region 21 b of the cover layer 21 onthe wiring pattern 20 has a low resistance, and a region 21 a on thesecond mask layer 17 has a high resistance. Therefore, the third wiringpattern 20 can be electrically connected to an upper layer wiringpattern via the low resistance region 21 b.

Next, with reference to FIGS. 2A to 2J, a method of manufacturing thesemiconductor device of the first embodiment will be described.

As shown in FIG. 2A, on the second interlayer insulating film 8 and plug9, the third interlayer insulating film 10 of low dielectric constantinsulating material is formed. If organic polymer is used as the lowdielectric constant insulating material, polymer dissolved in organicsolvent is spin-coated on the substrate surface. If carbon-containingsilicon oxide is used as the low dielectric constant insulatingmaterial, the third interlayer insulating film 10 can be formed byplasma enhanced chemical vapor deposition (PE-CVD). If porous insulatingmaterial is used as the low dielectric constant insulating material, thethird interlayer insulating film 10 can be formed by forming a hollowfilm through hydrolysis and condensation/polymerization by a sol-gelmethod, thermal decomposition of unstable components, formation of amold intermediate structure, and thermal decomposition of the moldintermediate structure. For this thermal composition, a heat treatmentat about 400° C. becomes necessary.

The first mask layer 11 of zirconium nitride is formed on the thirdinterlayer insulating film 10 by CVD. Source material to be used istetrakis diethylamino zirconium (Zr(N(C₂H₅)₂)₄) and ammonium (NH₃). Afilm forming temperature is 300 to 400° C. Ammonium is not necessarilyrequired to be added. Under these conditions, zirconium nitride is grownon silicon oxynitride, silicon nitride, silicon oxyfluoride, or lowdielectric constant organic polymer. The grown zirconium nitride is aninsulator. As will be later described, zirconium nitride grown on themetal surface under the same conditions is a conductor.

As shown in FIG. 2B, an opening 11 a corresponding to the second wiringpattern 12 a, 12 b shown in FIG. 1 is formed through the first masklayer 11. Etching the first mask layer 11 may be performed by dryetching using gas which contains chlorine (Cl₂) or hydrogen bromide(HBr).

As shown in FIG. 2C, by using the first mask layer 11 as a mask, thethird interlayer insulating film 10 is etched to form the wiring trench10 a. If the third interlayer insulating film 10 is made of organicpolymer, the third interlayer insulating film 10 may be etched by usingplasma of mixture gas of hydrogen and nitrogen.

As shown in FIG. 2D, a barrier metal layer 12A made of Ta, TaN, TiN orthe like is formed by sputtering, the barrier metal layer 12A coveringthe side wall and bottom of the wiring trench 10 a and the upper surfaceof the first mask layer 11. A seed layer 12B made of copper is formed onthe barrier metal layer 12A by sputtering. The seed layer 12B may beformed by sputtering using self-ionization plasma which provides goodstep coverage. The surface of the seed layer 12B is subjected toelectroplating to form a copper layer 12C.

As shown in FIG. 2E, CMP is performed to remove unnecessary portions ofthe copper layer 12C, seed layer 12B and barrier metal 12A. The secondlayer wiring pattern 12 is therefore left in the wiring trench 10 a, thesecond layer wiring pattern being made of the barrier metal layer 12A,seed layer 12B and main wiring material member 12C.

As shown in FIG. 2F, on and above the first mask layer 11 and secondlayer wiring pattern 12, the etching stopper layer 15, fourth interlayerinsulating film 16, second mask layer 17 and third mask layer 25 areformed in this order.

The etching stopper layer 15 made of silicon carbide or silicon nitridemay be formed by PE-CVD. If a silicon carbide film is to be formed,organic silane which contains methylsilane is used as source gas, and ifnecessary, gas such as a methane, nitrogen and helium is added. If asilicon nitride film is to be formed, monosilane, disilane, organicsilane or the like is used as the source of silicon, and nitrogen gas orammonium is used as the source of nitrogen.

The fourth interlayer insulating film 16 can be formed by a methodsimilar to the method of forming the third interlayer insulating film 10described with reference to FIG. 2A. The second mask layer 17 made ofzirconium nitride can be formed by a method similar to the method offorming the first mask layer 11 described with reference to FIG. 2A.

The third mask layer 25 is made of silicon carbide or silicon nitride orsilicon oxide. A method of forming the third mask layer 25 is similar tothe method of forming the etching stopper layer 15.

As shown in FIG. 2G, a resist pattern is formed on the third mask layer25 and the third mask layer 25 is partially etched to form an opening 25a corresponding to the wiring trench 18 shown in FIG. 1. After theresist pattern used for forming the opening 25 a is removed, a new maskpattern is formed on the second and third mask layers 17 and 25. Byusing this new mask pattern as a mask, the second mask layer 17 isetched to form an opening 17 a corresponding to the via hole 19 shown inFIG. 1. After the opening 17 a is formed, the resist pattern used as themask is removed.

As shown in FIG. 2H, by using the second and third mask layers 17 and 25as a mask, the fourth interlayer insulating film 16 exposed on thebottom of the opening 17 a is etched to the intermediate depth of thefourth interlayer insulating film 16 to form a recess 16 a. Etching thefourth interlayer insulating film 16 can be performed by a methodsimilar to the method of etching the third interlayer insulating film 10described with reference to FIG. 2C.

As shown in FIG. 21, by using the third mask layer 25 as a mask, thesecond mask layer 17 exposed on the bottom of the opening 25 a isetched.

As shown in FIG. 2J, by using the third and second mask layers 25 and 17as a mask, the fourth interlayer insulating film 16 is etched. Therecess 16 a shown in FIG. 21 becomes deeper and the via hole 19 istherefore formed. At this stage, the etching stopper film 15 is left onthe bottom of the via hole 19, and the fourth interlayer insulating film16 is further etched to the intermediate depth thereof in the area wherethe recess 16 a was not formed to thereby form the wiring trench 18.

The etching stopper film 15 exposed on the bottom of the via hole 19 isremoved to expose the upper surface of the second layer wiring pattern12. The etching stopper film 15 can be removed by dry etching mainlyusing gas which contains carbon fluoride. During this etching, the thirdmask layer 25 is also removed.

As shown in FIG. 1, the third layer wiring pattern 20 is buried in thewiring trench 18 and via hole 19. The wiring pattern 20 can be formed bya method similar to the method of forming the second layer wiringpattern 12 described with reference to FIGS. 2D and 2E.

The cover layer 21 made of zirconium nitride is formed on the secondmask layer 17 and third layer wiring pattern 20. The cover layer 21 canbe formed by a method similar to the method of forming the first masklayer 11 described with reference to FIG. 2A. As the zirconium nitridefilm is formed by this method, the region 21 b of the film on the wiringpattern 20 has a low resistance and the region 21 a on the second masklayer 17 has a high resistance. The low resistance region 21 b issubstantially a conductor and the high resistance region 21 a issubstantially an insulator.

The measurement results of electric resistance of actually formedzirconium nitride films will be described.

Zirconium nitride film was formed on a silicon oxide film and a titaniumnitride film by CVD using tetrakis diethylamino zirconium and ammoniumas source gas. The growth temperature of the zirconium nitride film wasset to 380° C.

The zirconium nitride film having a thickness of 20 nm or thinner andformed on the silicon oxide film became an insulating film having aspecific resistance of several thousands μΩcm or higher. In contrast,the zirconium nitride film having a thickness of 20 nm or thinner andformed on the titanium nitride film became an conductive film having aspecific resistance of about 300 μΩcm or lower. Even if the material ofthe underlying conductive layer is not titanium nitride but copper, thezirconium nitride film becomes a conductive film. This nature is alsotrue for a zirconium nitride not formed by CVD but formed by sputtering,vapor deposition or the like.

In the first embodiment, the first mask layer 11 of zirconium nitride isused as a mask during the process of etching the third interlayerinsulating film 10 described with reference to FIG. 2C. As compared to aconventional mask made of silicon nitride or the like, an etchingselectivity can be made large. It is therefore easy to work theinterlayer insulating film made of low dielectric constant insulatingmaterial.

As the material of the first mask layer 11 shown in FIG. 1, for example,silicon nitride is used. A specific dielectric constant of siliconnitride is higher than silicon oxide so that the effects of forming thethird interlayer insulating film 10 by using low dielectric constantinsulating material is diminished. The specific dielectric constants ofthe zirconium nitride films formed on the USG film and having athicknesses of about 15 nm and 30 nm were 2 to 3, and 3.5 to 4,respectively These specific dielectric constants are similar to or lowerthan that of silicon oxide. It is therefore possible to enhance theparasitic capacitance reduction effects between wiring lines.

In the first embodiment, although the first mask layer 11 is made ofzirconium nitride, it may be made of nitride which contains zirconium,titanium or hafnium as a constituent element.

FIG. 3 is a cross sectional view of a semiconductor device according toa second embodiment of the invention. Different points from thesemiconductor device of the first embodiment shown in FIG. 1 will bedescribed.

In the first embodiment, the material of the etching stopper layer 15used when the via hole 19 is formed in the fourth interlayer insulatingfilm 16 is silicon carbide or silicon nitride. In the second embodiment,instead of the etching stopper layer 15, an etching stopper layer 30 ofzirconium nitride is used. Similar to the cover film 21, in the etchingstopper layer 30, a region 30 b on the wiring pattern 12 a has a lowresistance and a region 30 a on the first mask layer 11 has a highresistance.

In the first embodiment, the etching stopper layer 15 exposed on thebottom of the via hole 19 is removed. In the second embodiment, theetching stopper layer 30 is left on the bottom of the via hole 19. Sincethe region 30 b on the wiring pattern 12 a has a low resistance, thesecond layer and third layer wiring patterns 12 a and 20 can beelectrically connected even if the etching stopper layer 30 is left.

By forming the etching stopper layer 30 by using zirconium nitride, anetching selectivity can be made large between the fourth interlayerinsulating film 16 made of low dielectric constant insulating materialand the etching stopper layer 30.

In the second embodiment, the etching stopper layer 30 made of zirconiumnitride is disposed between the second layer wiring pattern 12 a andfourth interlayer insulating film 16. This etching stopper layer 30functions as an adhesive layer so that tight adhesion between the wiringpattern 12 a made of copper and the fourth interlayer insulating film 16can be improved. Zirconium films having thicknesses of 5 nm and 15 nmwere formed on a copper surface and insulating films made of SiLK(trademark of Dow Chemical Company), low dielectric constant polymer,were formed on the zirconium nitride films. Tape tests were conducted.The SiLK insulating films were not scaled off. The SiLK insulating filmswere formed by coating SiLK and thereafter performing baking at 320° C.for 90 seconds and curing at 400° C. for 30 minutes.

In the second embodiment, the upper surface of the second wiring pattern12 a is covered with the etching stopper layer 30 made of zirconiumnitride. This etching stopper layer 30 also functions as a barrier layerfor preventing copper of the wiring pattern 12 a from diffusing into thefourth interlayer insulating film 16. With reference to FIGS. 7 and 8,the barrier function of the zirconium nitride film will be described.

FIG. 7 shows the breakdown voltage characteristics of a USG film and thelamination structure of a USG film and a zirconium nitride film. Theabscissa represents an electric field in the unit of “MV/cm” and theordinate represents a leak current in the unit of “A”.

First and second samples were prepared, the first sample having a USGfilm and a copper electrode formed in this order on a silicon substrate,and the second sample having a USG film, a zirconium nitride film and acopper electrode formed in this order on a silicon substrate. Thethickness of the USG film of the first sample is 47 nm. The thickness ofthe USG film of the second sample is 47 nm and the thickness of thezirconium nitride film is 3.5 nm. A black square in the graph shows aleak current of the first sample, and a black circle shows a leakcurrent of the second sample.

The first sample had a dielectric breakdown when the electric fieldincreased to 7.4 MV/cm. The electric field increase speed was 0.1MV/cm·s. The dielectric breakdown is considered to occur because of thediffusion of copper atoms in the copper electrode into the USG film. Thesecond sample had a dielectric breakdown when the electric fieldincreased to 11.6 MV/cm. By inserting the zirconium nitride film betweenthe copper electrode and USG film, the breakdown voltage can be raised.This suggests that the zirconium nitride film suppresses copper fromdiffusing from the copper electrode to the USG film.

By inserting the zirconium nitride film, the leak current itself can bereduced.

FIG. 8 shows average times to dielectric breakdown of third to fifthsamples. The third sample has the structure that a USG film of 47 nmthick and a copper electrode are formed in this order on a siliconsubstrate. The fourth sample has the structure that a thermally oxidizedfilm (Tox) of 100 nm thick and a copper electrode are formed in thisorder on a silicon substrate. The fifth sample has the structure that aUSG film of 47 nm thick, a zirconium nitride film of 3.5 nm thick and acopper electrode are formed in this order on a silicon substrate.

The abscissa of FIG. 8 represents an electric field in the unit of“MV/cm” and the ordinate represents an average time to dielectricbreakdown in the unit of “second”. An environmental temperature was setto 150° C. By inserting the zirconium nitride film between the USG filmand copper electrode, the average time to dielectric breakdown isprolonged under the same electric field condition. This suggests thatthe zirconium nitride film suppresses the diffusion of copper.

FIG. 4 is a cross sectional view of a semiconductor device according toa third embodiment of the invention. Different points from thesemiconductor device of the first embodiment shown in FIG. 1 will bedescribed.

In the first embodiment, the first mask layer 11 and etching stopperlayer 15 are in direct contact with each other as shown in FIG. 1. Inthe third embodiment, between the first mask layer 11 and etchingstopper layer 15, a sacrificial film 35 is disposed which is made ofinorganic insulating material containing silicon as its constituentelement, such as USG, silicon carbide and silicon nitride. Withreference to FIGS. 5A to 5E, the method of manufacturing thesemiconductor device of the third embodiment will be described

As shown in FIG. 5A, the layers up to the first mask layer 11 are formedby a method similar to the first embodiment method described withreference to FIG. 2A. The sacrificial film 35 of USG is formed on thefirst mask layer 11. The USG film can be formed by CVD using silane ortetraethoxysilane (TEOS) as source gas, oxygen (O₂) or NN₂O as oxidizinggas, and argon (Ar) or nitrogen (N₂) as carrier gas. The sacrificialfilm 35 may be made of silicon carbide or silicon nitride.

As shown in FIG. 5B, an opening 11 a for forming a wiring trench isformed through the sacrificial film 35 and first mask layer 11.

As shown in FIG. 5C, by using the sacrificial film 35 and first masklayer 11 as a mask, the third interlayer insulating film 10 is etched toform the wiring trench 10 a.

As shown in FIG. 5D, a barrier metal layer 12A and a seed layer 12B areformed on the inner surface of the wiring trench 10 a and on the surfaceof the sacrificial film 35. A main wiring material member 12C is formedon the seed layer 12B by plating, the main wiring material member 12Cbeing buried in the wiring trench 10 a.

As shown in FIG. 5E, CMP is performed to remove unnecessary portions ofthe main wiring material member 12C, seed layer 12B and barrier metallayer 12A to leave the wiring pattern 12 in the wiring trench 10 a. Inthis case, since the first mask layer 11 of zirconium nitride is coveredwith the sacrificial film 35, the first mask layer 11 is prevented frombeing exposed in the CMP environment. The first mask layer 11 enhancesthe tight adhesion between the third interlayer insulating film 10 andsacrificial film 35.

A tight adhesion strength test (mELT: Modified Edge Lift-off Test) wasperformed for two types of samples having SiLK insulating films of 150nm thick and 450 nm thick formed on silicon oxide films thermallyoxidized. The K values were about 0.21 and 0.30, respectively. Incontrast, the sample having a zirconium nitride film of 4 nm thickformed on a silicon oxide film thermally oxidized and a SILK insulatingfilm of 250 nm thick formed on the zirconium nitride film had a K valueof 0.40 or higher. It can be understood that the zirconium nitride filmimproves the tight adhesion between the silicon oxide film and SiLKinsulating film.

FIG. 6 is a cross sectional view of a semiconductor device according toa fourth embodiment of the invention. The cross sectional shape of thesemiconductor device of the fourth embodiment is the same as that of thesemiconductor device of the first embodiment shown in FIG. 1. In thefirst embodiment, the third and fourth interlayer insulating films 10and 16 are made of low dielectric constant insulating material such asSiLK. In the fourth embodiment, the third and fourth interlayerinsulating films 10 and 16 are made of high resistance zirconiumnitride.

In the fourth embodiment, the first mask layer 11 is made of USG,silicon carbide or silicon nitride. By using the first mask layer 11 asa mask, the third interlayer insulating film 10 of zirconium nitride isetched to form the wiring trench 10 a. Zirconium nitride can bedry-etched by using gas which contains chlorine (Cl₂) or bromidehydrogen (HBr).

The third layer wiring pattern 20 is formed by the dual damascene methoddescribed with reference to FIGS. 2F to 2J. In the fourth embodiment,the third mask layer 25 shown in FIGS. 2F to 2I is made of the samematerial as that of the etching stopper layer 15, and the second masklayer 17 is made of USG, silicon carbide or silicon nitride whichever isdifferent from the material of the third mask layer 25.

In the fourth embodiment, zirconium nitride is used as the material ofthe third and fourth interlayer insulating films The dielectric constantof zirconium nitride can be made lower than that of silicon oxide. It istherefore possible to reduce the parasitic capacitance between wiringlines.

In an crossed area between another wiring pattern disposed in the samewiring layer as that of the second layer wiring pattern 12 a and anotherwiring pattern disposed in the same wiring layer as that of the thirdlayer wiring pattern 20, the other wiring patterns can be electricallyinsulated by the lamination structure of the etching stopper layer 15and third interlayer insulating film 10. In order to obtain sufficientparasitic capacitance reduction effects between the other wiringpatterns, it is preferable to adopt the structure that the thirdinterlayer insulating film 10 occupies a half or more of the distancebetween the other wiring patterns in the crossed area.

Since a zirconium nitride film can be formed without using plasma, themanufacture processes can be simplified. Instead of a zirconium nitridefilm, a film made of nitride which contains zirconium, titanium orhafnium as a constituent element may be used.

The present invention has been described in connection with thepreferred embodiments. The invention is not limited only to the aboveembodiments. It is apparent that various modifications, improvements,combinations, and the like can be made by those skilled in the art.

1. A method of manufacturing a semiconductor device, comprising stepsof: forming a first insulating film consisting of insulating material ona semiconductor substrate; forming a second insulating film consistingof insulating metal nitride on said first insulating film; patterningsaid second insulating film; and etching said first insulating film byusing said second insulating film as a mask.
 2. A method ofmanufacturing a semiconductor device according to claim 1, wherein saidsecond insulating film consists of nitride containing as a constituentelement one element selected from a group consisting of zirconium,titanium and hafnium.
 3. A method of manufacturing a semiconductordevice, comprising steps of: forming a first insulating film on asemiconductor substrate, at least a surface layer of said firstinsulating film consisting of metal nitride; forming a second insulatingfilm consisting of inorganic insulating material containing silicon onsaid first insulating film; forming a recess in a lamination structureof said second and first insulating films; depositing a conductive filmconsisting of conductive material on said second insulating film, saidconductive film being filled in said recess; and polishing saidconductive film until said second insulating film is exposed, andleaving a portion of said conductive film in said recess.
 4. A method ofmanufacturing a semiconductor device according to claim 3, wherein saidfirst insulating film includes a low dielectric constant film consistingof insulating material having a dielectric constant lower than adielectric constant of said second insulating film and a nitride layerconsisting of insulating metal nitride and formed on the low dielectricconstant film.
 5. A method of manufacturing a semiconductor deviceaccording to claim 3, wherein the insulating metal nitride contains as aconstituent element one element selected from a group consisting ofzirconium, titanium and hafnium.